/Engine/Source/Runtime/AudioMixer/Public/AudioMixerSubmix.h
Encode a source and sum it into the mixed soundfield.
void MixInSource ( const [ISoundfieldAudioPacket](API\Runtime\AudioExtensions\ISoundfieldAudioPacket) & InAudio, const [ISoundfieldEncodingSettingsProxy](API\Runtime\AudioExtensions\ISoundfieldEncodingSettingsProxy) & InSettings, [ISoundfieldAudioPacket](API\Runtime\AudioExtensions\ISoundfieldAudioPacket) & PacketToSumTo )